15Investigating depression-like conditions in animals is methodologically challenging, but also revealed that horses scored as withdrawn then remained significantly likely to display the 24 behaviour. We measured sucrose intake, a classic measure of anhedonia never previously 25 applied to horses. Flavoured sugar blocks, novel to these subjects, were mounted in each stall 26 and weighed 3h, 8h, 24h and 30h after provision. We predicted that if affected by depression-27 like states, the most withdrawn horses would consume the least sucrose. This prediction was 28 met (F1,18 = 4.65, two tailed p = 0.04). This pattern could, however, potentially reflect general 29 appetite levels and/or food neophobia. To control for these confounds, hay consumption was 30 measured over 5 days, as were subjects' latencies to eat a meal scented with a novel odour. 31Although low hay consumption and long latencies to eat scented food did predict low sucrose 32 consumption, statistically controlling for these confounds did not eliminate the relationship 33 between being withdrawn and consuming less sucrose (although reducing it to a strong trend): Table 1) that include low, hopeless moods, 49"not caring", social withdrawal, and fatigue (APA, 2013). These are present for many days or Miller et al., 2007, and sub-57 normal levels e.g. Strickland et al., 2002). 58In terms of aetiology, a common trigger is chronic stress, for instance that arising from 59 aversive life events or chronic pain or illness ( e.g. Banks and Kerns, 1996; Blackburn-Munro 60 and Blackburn-Munro, 2001;Tafet and Bernardini, 2003; Munce et al., 2006;Siegrist, 2008; 61 Hammen et al., 2009; APA, 2013). Two types of cognitive change can often be observed before 62 the illness fully develops, and these may act as mediators in some subjects, being hypothesised 63 to help cause the onset and/or maintenance of the disease (Beck, 1967; Gotlib and 64 Krasnoperova, 1998). One is 'learned helplessness', which is proposed to occur "when highly 65 5 desired outcomes are believed improbable or highly aversive outcomes are believed probable, 66 and the individual comes to expect that no response in his repertoire will change their 67 likelihood" (Abramson et al., 1978). The second involves negative biases in attention, memory 68 and/or judgment (Beck, 1967; MacLeod and Byrne, 1996; Gotlib and Krasnoperova, 1998). 69Thus depressed people are prone for example, to judge ambiguous stimuli as being unlikely to 70 be positive ('cognitive pessimism'), and to recall unpleasant memories more readily than 71 pleasant ones. 72The symptoms of depression may not be unique to humans. A Web of Science literature 73 search using the terms "rats" OR "mice" OR "monkeys" AND "depression" yielded over Engel, 2002 p174, Brune et al., 2006 Ferdowsian et al., 2011; Hennessy et al., 2014) 96 and maternally deprived monkeys ( e.g. Harlow and Suomi, 1974;Suomi et al., 1975; Hennessy 97 et al., 2014). Horses, too, have been suggested to sometimes display depression-li...

No abstract

Attention is described as the ability to process selectively one aspect of the environment over others. In this study, we characterized horses' spontaneous attention by designing a novel visual attention test (VAT) that is easy to apply in the animal's home environment. The test was repeated over three consecutive days and repeated again 6 months later in order to assess inter-individual variations and intra-individual stability. Different patterns of attention have been revealed: 'overall' attention when the horse merely gazed at the stimulus and 'fixed' attention characterized by fixity and orientation of at least the visual and auditory organs towards the stimulus. The individual attention characteristics remained consistent over time (after 6 months, Spearman correlation test, P < 0.05). The validity of this novel test as a predictor of individual attentional skills was assessed by comparing the results, for the same horses, with those obtained in both a 'classical' experimental attention test the 'five-choice serial reaction time task' (5-CSRTT) and a work situation (lunge working context). Our results revealed that (i) individual variations remained consistent across tests and (ii) the VAT attention measures were not only predictive of attentional skills but also of learning abilities. Differences appeared however between the first day of testing and the following test days: attention structure on the second day was predictive of learning abilities, attention performances in the 5-CSRRT and at work. The VAT appears as a promising easy-to-use tool to assess animals' attention characteristics and the impact of different factors of variation on attention.

As visual attention is an intrinsic part of social relationships, and because relationships are built on a succession of interactions, their establishment involves learning and attention. The emotional, rewarding or punishing, content can modulate selective attention. In horses, the use of positive/negative reinforcement during training determines short and long-term human-horse relationships. In a recent study in horses, where either food or withers' grooming were used as a reward, it appeared that only the food-rewarded horses learned the task and show better relationship with humans. In the present study, we hypothesized that this differential effect of grooming/food rewards on learning performances could be due to attentional processes. Monitoring, gazes and behaviors directed towards the trainer revealed that the use of a food reward (FR) as positive reinforcement increased horses' selective attention towards their trainer. Conversely, horses trained with grooming reward (GR) expressed more inattentive responses and did not show a decrease of “agitated” behavior. However, individual plotting of attention vs. rate of learning performances revealed a complex pattern. Thus, while all FR horses showed a “window” of attention related to faster learning performances, GR horses' pattern followed an almost normal curve where the extreme animals (i.e., highest and lowest attention) had the slowest learning performances. On the other hand, learning was influenced by attention: at the end of training, the more attentive horses had also better learning performances. This study, based on horses, contributes to the general debate on the place of attentional processes at the interface of emotion and cognition and opens new lines of thought about individual sensitivities (only individuals can tell what an appropriate reward is), attentional processes and learning.

BackgroundAdverse early-life experience might lead to the expression of abnormal behaviours in animals and the predisposition to psychiatric disorder (e.g. major depressive disorder) in Humans. Common breeding processes employ weaning and housing conditions different from what happens in the wild.MethodsThe present study, therefore, investigated whether birth origin impacts the possible existence of spontaneous atypical/abnormal behaviours displayed by 40 captive-born and 40 wild-born socially-housed cynomolgus macaques in farming conditions using an unbiased ethological scan-sampling analysis followed by multifactorial correspondence and hierarchical clustering analyses.ResultsWe identified 10 distinct profiles (groups A to J) that significantly differed on several behaviours, body postures, body orientations, distances between individuals and locations in the cage. Data suggest that 4 captive-born and 1 wild-born animals (groups G and J) present depressive-like symptoms, unnatural early life events thereby increasing the risk of developing pathological symptoms. General differences were also highlighted between the captive- and wild-born populations, implying the expression of differential coping mechanisms in response to the same captive environment.ConclusionsBirth origin thus impacts the development of atypical ethologically-defined behavioural profiles, reminiscent of certain depressive-like symptoms. The use of unbiased behavioural observations might allow the identification of animal models of human mental/behavioural disorders and their most appropriate control groups.

Chronic pain is thought to affect patients’ cognitive functioning, including attention. Loss of attention is likely to have an impact on the execution of daily tasks, and, therefore, to have negative effects. However, relationships between chronic pain and cognitive deficits are still debated. Pre-clinical studies using laboratory animals prove useful to model pain-related cognitive impairment, but animal models had to predict effects in the real world. This study investigates attentional engagement of domestic horses by comparing observations in a home setting and evaluations of vertebral disorders. We found that lower attentional engagement and the level of back disorders were correlated. Two different evaluation techniques of the state of horses’ spines gave similar results. We suggest that novel animal models would prove useful for identifying spontaneous behaviours indicative of chronic pain. We suggest that more ethological studies in human patients’ home environments would help to improve our understanding of the processes involved. Finally, these results yield interesting indications for evaluating animal welfare, as attentional engagement could become a reliable indicator of chronic pain and thus a useful tool for identification of suffering individuals.

Some captive/domestic animals respond to confinement by becoming inactive and unresponsive to external stimuli. Human inactivity is one of the behavioural markers of clinical depression, a mental disorder diagnosed by the co-occurrence of symptoms including deficit in selective attention. Some riding horses display 'withdrawn' states of inactivity and low responsiveness to stimuli that resemble the reduced engagement with their environment of some depressed patients. We hypothesized that 'withdrawn' horses experience a depressive-like state and evaluated their level of attention by confronting them with auditory stimuli. Five novel auditory stimuli were broadcasted to 27 horses, including 12 'withdrawn' horses, for 5 days. The horses' reactions and durations of attention were recorded. Non-withdrawn horses reacted more and their attention lasted longer than that of withdrawn horses on the first day, but their durations of attention decreased over days, but those of withdrawn horses remained stable. These results suggest that the withdrawn horses' selective attention is altered, adding to already evidenced common features between this horses' state and human depression.

Electroencephalography (EEG) that has been extensively studied in humans presents also a large interest for studies on animal brain processes. However, since the quality of the recordings is altered by muscular activity, most EEG recordings on animals are obtained using invasive methods with deeply implanted electrodes. This requires anesthesia and can thus only be used in laboratory or clinical settings. As EEG is a very useful tool both for detecting brain alterations due to diseases or accidents and to evaluate the arousal and attentional state of the animal, it seemed crucial to develop a tool that would make such recordings possible in the horse’s home environment, with a freely moving horse. Such a tool should neither be invasive nor cause discomforts to the horse as the usual other practice which consists, after shaving the zone, in gluing the electrodes to the skin. To fulfill these requirements, we developed a novel EEG headset adapted to the horse’s head that allows an easy and fast positioning of the electrodes and that can be used in the home environment on a freely moving horse. In this study, we show that this EEG headset allows to obtain reliable recordings, and we propose an original evaluation of an animal’s “EEG profile” that allows comparisons between individuals and situations. This EEG headset opens new possibilities of investigation on horse cognition, and it can also become a useful tool for veterinarians to evaluate cerebral disorders or check the anesthesia level during a surgery.